Millions of
Years of Interaction with Evolutionary Pressures
Dr. Moalem
depicts the pregnancy as “an evolutionary miracle that just needs to be helped
along.” Throughout pages 192 to 196, Dr. Moalem states that big brains and
bipedalism are major human traits compared to “any of our genetic cousins,”
such as chimps, other apes, and monkeys. This evolutionary history of human is related
to the Big Idea 1 (The process of evolution drives the diversity and unity of
life). However, big brains and bipedalism are “favor adaptions that made
reproduction more dangerous.” Related to the concepts of survival and
reproduction, explain why big brains and bipedalism are selected as favor
adaptations in human history.
In addition,
there are two hypotheses about bipedalism: savanna hypothesis and Alister
Hardy’s theory of “an aquatic ape. ” Define and contrast these two hypotheses.
Lastly, the idea
of water birth supports Hardy’s theory of “an aquatic ape.” Research the advantages and disadvantages of water birth. Consider Dr. Myrtle McGraw’s claim:
“The ‘water-friendly’ behavior [of human newborns] is instinctual and lasts
until babies are about four months old, when the movements become less
organized” (204).
The aquatic ape theory resulted from the fact that many human ancestors spent time in and around water for survival. As Moalem mentions, "their ability to survive on land and water gave them twice as many options to avoid predators" (199). The aquatic ape theory could explain many features we humans have today. For example, it explains why we lost fur, why our noses are more prominent, and also, why fat is attached to our skin. All of these previously mentioned traits occurred in order to help us survive in aquatic environments- to streamline faster, to dive better, and to use less energy to swim.
ReplyDeleteThis process of acquiring favorable traits is known as natural selection, which relates to Big Idea 1, which states the process of evolution drives the diversity and unity of life. In natural selection, first their must be variation in traits among a population. Then, due to selective pressures, one trait is favored over the other. This allows those with the selective trait to survive and reproduce better than those without the selective trait, thus giving a selective advantage to those with the trait. Over time, the population can adapt to its environment and will be able to survive and reproduce more easily.
In humans, "water acted as an agent of selection" (201). Humans could survive and reproduce better when able to use water to hide from land predators and also to dive for food. Therefore, humans with little hair, more prominent noses, and more fat were selected for in this environment. As time went on, the population of humans evolved to be able to use water to their advantage. The selection of bipedalism also arose, leading to advantages in the water, by being able to stand and breathe while in deeper waters. However, this also causes an issue in child birth. Bipedalism changed our pelvis and twisted the birth canal making child birth much harder, especially with human's bigger brains. To fix this, water birthing became a solution. Since water made it easier for aquatic apes to give birth with small pelvic openings, the same should work with humans. Thus, helping humans survive and reproduce.
On the other hand, the savanna hypothesis suggests that our ancestors moved into the savanna and had to find new ways to live. In order to live in this environment, they had to "scan horizons for predators" (197), which lead to bipedalism, work together, which lead to bigger brains, and try not to overheat, which led to the loss of fur. The savanna theory is the conventional theory and can be proved true in numerous situations, however, there are many gaps in the hypothesis, allowing the aquatic ape theory to hold true in situations as well. The History Planet (http://historyplanet.wordpress.com/2010/03/17/aquatic-ape-theory/) acknowledges that the aquatic ape theory is far from proven, but provides significant evidence for its validity. The History Planet mentions that "Of all man’s ancestors, Home Erectus, experienced the largest singe brain growth. Most Homo Erectus finds have been found along coastal areas and Erectus is accepted by mainstream archaeology to be a shore dweller" This idea of living by the shore and having bigger brains supports the Aquatic Ape Theory rather than the savanna hypothesis which thought that since the apes had to make tools in the savanna, they adapted to having bigger brains.
There are many advantages and disadvantages to water birthing. Some risks of water birthing are brain injury from lack of water underwater, electrolyte problems from the baby swallowing water, and serious infection from contaminated water (http://www.webmd.com/baby/guide/water-birth). However, in most cases, the advantages outweigh the disadvantages. Some advantages include reduction in risk of vaginal tearing, reduction in need for anesthesia, and a more relaxed environment. Thus, even with the great technology we have today, water birthing proves to have some advantages over birthing in high technology hospitals.
(Posted by Lindsay Pontello, lpontel4@students.d125.org)